The move comes after outside studies linked those secondary illnesses — along with unprovoked seizures and diseases of the hypothalamus and pituitary glands — to traumatic brain injury.

Veterans who prove their TBI is service-related won’t have to prove those secondary issues also stem from combat wounds, creating a quicker path to receive disability payments. As with any claim, the amount for payouts will still depend on the severity of the health issues.

According to Veterans Benefits Administration statistics, about 73,000 veterans are currently receiving disability payments for service-connected brain injuries. But outside experts estimate that one in five recent combat veterans — more than 500,000 individuals — may suffer from some level of TBI.

VA officials could not say how many veterans may suffer from both TBI and one of the five new presumptive illnesses.

However, they categorized the number of affected cases as “small” and said they do not expect the new rule to have a noticeable change on the claims inventory or backlog.

They also noted that the change does not create any new entitlements for veterans, only speeds up awards for injuries already covered under VA rules. In the past, veterans had to submit medical documentation linking the TBI and the secondary condition before claims would be approved.

The new rules go into effect in mid-January.

Although the outside research focused on younger veterans, the new policy covers veterans of all generations.